(1) Field of the Invention
The present invention relates to rubber-reinforcing aromatic polyamide fiber cords. More particularly, the invention relates to rubber-reinforcing aromatic polyamide fiber cords used as reinforcements in carcass layers and belt layers of tires, hoses, belts, etc.
(2) Related Art Statement
Heretofore, a majority of fiber-reinforcing rubber structures have been reinforced by fiber cords made of materials such as rayon, nylon, polyester, etc. Recently, aromatic polyamide fiber cords have begun to be used as reinforcements for rubber articles such as tires, hoses, belts, etc. This is because as compared with the conventional organic synthetic fibers, the aromatic polyamide fibers have higher tenacity, higher modulus, and excellent heat resistance and dimensional stability.
Although aromatic polyamide fibers have the above-mentioned merits, they have a demerit that they have far poorer compression fatigue resistance as compared with other organic synthetic fibers. Under the circumstances, research has been done to improve the compression fatigue resistance of the aromatic polyamide fibers. As one of coutermeasures, a method of increasing the number of twists of cords has conventionally been known. Indeed, the compression fatigue resistance is certainly improved by increasing the number of twists, but on the other hand, the tenacity of the cords is simultaneously lowered. Thus, there occurs a problem that the merit of the aromatic polyamide fibers have higher tenacity is reduced.